MDEV-21318: Wrong results with window functions and implicit grouping

The issue here is for degenerate joins we should execute the window
function but it is not getting executed in all the cases.

To get the window function values window function needs to be executed
always. This currently does not happen in few cases
where the join would return 0 or 1 row like
  1) IMPOSSIBLE WHERE
  2) MIN/MAX optimization
  3) EMPTY CONST TABLE

The fix is to make sure that window functions get executed
and the temporary table is setup for the execution of window functions

sql/sql_select.h

@@ -1057,6 +1057,7 @@ protected:
   void restore_query_plan(Join_plan_state *restore_from);
   /* Choose a subquery plan for a table-less subquery. */
   bool choose_tableless_subquery_plan();
+  void handle_implicit_grouping_with_window_funcs();
 
 public:
   JOIN_TAB *join_tab, **best_ref;